MQME-28E-P
Current:
20A
Technical Specification
BASIC OPERATION AND FEATURES
The MQME-28E-P is a multi-stage differential-mode and common-
mode passive EMI filter designed to interface a power source with
one or more SynQor DC/DC converters (or other loads that create
EMI). Each stage of this filter is well damped to avoid resonances
and oscillations, and only X7R multi-layer ceramic capacitors are
used. Figure 1 shows the typical differential and common-mode
attenuation provided by this filter when the source impedance is
50Ω
to chassis ground on each input line.
The MQME-28E-P EMI filter includes a large bulk capacitor (also
X7R) with a series damping resistor to correct for the unstabilizing
effect of a converter’s negative input resistance. A white paper
discussing this negative input resistance and the need for corrective
damping can be found on the SynQor website (see Input System
Instability application note). Figure 2 shows the magnitude of the
filter’s output impedance when the filter input is connected to a
stiff voltage source.
The input voltage surge and spike compliance matrix shown on
Page 8 displays the worst case requirements listed in various
28V Military (Vehicle and Aircraft) and Civil Aircraft standards.
The MQME-28E-P EMI filter is designed to handle all of the
short duration voltage spike requirements of these standards
(with certain assumptions regarding DEF-STAN 61-5). Some of
the long duration voltage surge requirements remain within the
50V maximum transient rating of a SynQor MQFL-28 DC/DC
converter. The others require the transient suppression circuitry of
an MQME-28-T EMI filter to protect the converter from an over-
voltage condition. If MQFL-28E or MQFL-28VE converters are
used, voltage surges as high as 80V can be tolerated without the
need for this transient suppression circuitry.
When used with SynQor’s DC/DC converters, the MQME-28E-P
EMI filter is designed to pass all of the relevant MIL-STD-461C/
D/E requirements to their most stringent limits. The MIL-STD-461
Compliance Matrix Table on Page 7 lists these requirements and
describes the setup used to pass them. Figures 3 - 6 show results
from selected conductive and radiated emissions tests.
The filter is also designed to pass the waveform types and
applications specified in RTCA/DO-160E Section 22 (Lightning
Induced Transient Susceptibility) to Level 4 (some waveforms/
applications require the MQME-28-T filter and/or external
transient suppression circuitry). The Section 22 Compliance
Matrix Table on Page 9 lists these waveforms and applications
and describes the setup used to pass them.
A typical application would place the MilQor filter close to the
input of the DC/DC converter, with the cases of the filter and
the converter connected together through a ground plane. Both
cases are electrically conductive, so connection to the cases can
be made with the fasteners used to secure the device.
Do not connect the outputs of multiple MQME-28E-P filters in
parallel. Connecting filters in this manner may result in slightly
unequal currents to flow in the positive and return paths of each
filter. These unequal currents may cause the internal common-
mode chokes to saturate and thus cause degraded common-mode
rejection performance.
Product # MQME-28E-P
Phone 1-888-567-9596
www.synqor.com
Doc.# 005-0005135 Rev. A
03/18/09
Page 6
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